1. Field of the Invention
This invention lies in the field of laboratory apparatus for biochemical analyses. In particular, this invention addresses the needs of applying stains to electrophoresis slab gels used in the analysis of biochemical samples, the stains serving to permit visualization of bands on the gels that represent the components of the samples.
2. Description of the Prior Art
The widely used laboratory procedure known as gel electrophoresis utilizes the ability of solutes such as proteins, nucleic acids, and biological molecules in general to respond to an electric field by migrating through a gel across which the field is imposed, the migration occurring at different rates for different solute molecules depending on the size and charge of the molecule. A biological sample to be analyzed is placed at one end of the gel and the electric field is maintained across the gel until the solutes in the sample are separated into discrete bands distributed along the length of the gel. The location of each band defines the solute contained within that band, and in some cases, the intensity of the band serves as an indication of the amount of that solute present in the sample. Gels in the form of rectangular slabs offer the advantage of allowing several samples to be analyzed simultaneously along adjacent parallel migration paths in the same gel. Also favorable is the fact that electropherograms in slab gels are easily observed and read visually, allowing comparisons among samples and between samples and controls.
Most solutes of interest in biological samples cannot be visualized or observed either by the naked eye or by instrumentation without first being stained with a dye. It is also often necessary to fix the gel to render the gel stable for extended periods of time. Staining and fixing are time-consuming procedures, and efficiency often requires that these procedures be applied to several slab gels at the same time. For an accurate reading of the bands, the stain must be uniformly applied across any given slab gel as well as among different slab gels that are processed simultaneously.
One type of apparatus that is commonly used for staining and fixing of gels is a rocking apparatus in which the gel is placed on a rectangular tray together with the staining or fixing reagent and the tray is tipped from side to side to cause the reagent to move back and forth across the gel. Another known type of apparatus is a shaker in which the gel is again placed on a tray and the tray is shaken with a circular motion while being held horizontal. In both cases, the movement, whether rocking or shaking, is provided by a table that supports the trays and moves accordingly. The disadvantage of rocking or shaking tables is that they are bulky, expensive and consume high amounts of energy.